Editorial: tertiary lymphoid organs (TLOs): powerhouses of disease immunity

No abstract available

Using phase-change materials to switch the direction of reflectionless light propagation in non-PT-symmetric structures

We introduce a non-parity-time-symmetric three-layer structure, consisting of a gain medium layer sandwiched between two phase-change medium layers for switching of the direction of reflectionless light propagation. We show that for this structure unidirectional reflectionlessness in the forward direction can be switched to unidirectional reflectionlessness in the backward direction at the optical communication wavelength by switching the phase-change material Ge2Sb2Te5 (GST) from its amorphous to its crystalline phase. We also show that it is the existence of exceptional points for this structure with GST in both its amorphous and crystalline phases which leads to unidirectional reflectionless propagation in the forward direction for GST in its amorphous phase, and in the backward direction for GST in its crystalline phase. Our results could be potentially important for developing a new generation of compact active free-space optical devices. We also show that phase-change materials can be used to switch photonic nanostructures between cloaking and superscattering regimes at mid-infrared wavelengths. More specifically, we investigate the scattering properties of subwavelength three-layer cylindrical structures in which the material in the outer shell is the phase-change material GST. We first show that, when GST is switched between its amorphous and crystalline phases, properly designed electrically small structures can switch between resonant scattering and cloaking invisibility regimes. The contrast ratio between the scattering cross sections of the cloaking invisibility and resonant scattering regimes reaches almost unity. We then also show that larger, moderately small cylindrical structures can be designed to switch between superscattering and cloaking invisibility regimes, when GST is switched between its crystalline and amorphous phases. The contrast ratio between the scattering cross sections of cloaking invisibility and superscattering regimes can be as high as ~ 93%. Our results could be potentially important for developing a new generation of compact reconfigurable optical devices

Artery tertiary lymphoid organs control multi-layered territorialized atherosclerosis B cell responses in aged ApoE-/- mice

Objective: Explore aorta B cell immunity in aged ApoE-/- mice. Approach and Results: Transcript maps, FACS, immunofluorescence analyses, cell transfers, and Ig-ELISPOT assays showed multi-layered atherosclerosis B cell responses in artery tertiary lymphoid organs (ATLOs). Aging-associated aorta B cell-related transcriptomes were identified and transcript atlases revealed highly territorialized B cell responses in ATLOs versus atherosclerotic lesions: ATLOs showed upregulation of bona fide B cell genes including Cd19, Ms4a1 (Cd20), Cd79a/b, and Ighm though intima plaques preferentially expressed molecules involved in non-B effector responses towards B cell-derived mediators, i.e. Fcgr3 (Cd16), Fcer1g (Cd23), and the C1q family. ATLOs promoted B cell recruitment. ATLO B-2 B cells included naïve, transitional, follicular, germinal center, switched IgG1+, IgA+, and IgE+ memory cells, plasmablasts, and long-lived plasma cells (PCs). ATLOs recruited large numbers of B-1 cells whose subtypes were skewed towards IL-10+ B-1b cells versus IL-10- B-1a cells. ATLO B-1 cells and PCs constitutively produced IgM and IgG and a fraction of PCs expressed IL-10. Moreover, ApoE-/- mice showed increased germinal center B cells in renal lymph nodes, IgM-producing PCs in the bone marrow, and higher IgM and anti-MDA-LDL IgG serum titers. Conclusions: ATLOs orchestrate dichotomic, territorialized, and multi-layered B cell responses in the diseased aorta; germinal center reactions indicate generation of autoimmune B cells within the diseased arterial wall during aging

Broadband near total light absorption in non-PT-symmetric waveguide-cavity systems

We introduce broadband waveguide absorbers with near unity absorption. More specifically, we propose a compact non-parity-time-symmetric perfect absorber unit cell, consisting of two metal-dielectric-metal (MDM) stub resonators with unbalanced gain and loss side-coupled to a MDM waveguide, based on unidirectional reflectionlessness at exceptional points. With proper design, light can transport through the perfect absorber unit cell with reflection close to zero in a broad wavelength range. By cascading multiple unit cell structures, the overall absorption spectra are essentially the superposition of the absorption spectra of the individual perfect absorber unit cells, and absorption of ∼ 100% is supported in a wide range of frequencies

Slow-light enhanced subwavelength plasmonic waveguide refractive index sensors

We introduce slow-light enhanced subwavelength scale refractive index sensors which consist of a plasmonic metal-dielectric-metal (MDM) waveguide based slow-light system sandwiched between two conventional MDM waveguides. We first consider a MDM waveguide with small width structrue for comparison, and then consider two MDM waveguide based slow light systems: a MDM waveguide side-coupled to arrays of stub resonators system and a MDM waveguide side-coupled to arrays of double-stub resonators system. We find that, as the group velocity decreases, the sensitivity of the effective index of the waveguide mode to variations of the refractive index of the fluid filling the sensors as well as the sensitivities of the reflection and transmission coefficients of the waveguide mode increase. The sensing characteristics of the slow-light waveguide based sensor structures are systematically analyzed. We show that the slowlight enhanced sensors lead to not only 3.9 and 3.5 times enhancements in the refractive index sensitivity, and therefore in the minimum detectable refractive index change, but also to 2 and 3 times reductions in the required sensing length, respectively, compared to a sensor using a MDM waveguide with small width structure

Switching of the direction of reflectionless light propagation at exceptional points in non-PT-symmetric structures using phase-change materials

We introduce a non-parity-time-symmetric three-layer structure, consisting of a gain medium layer sandwiched between two phase-change medium layers for switching of the direction of reflectionless light propagation. We show that for this structure unidirectional reflectionlessness in the forward direction can be switched to unidirectional reflectionlessness in the backward direction at the optical communication wavelength by switching the phase-change material Ge2Sb2Te5 (GST) from its amorphous to its crystalline phase. We also show that it is the existence of exceptional points for this structure with GST in both its amorphous and crystalline phases which leads to unidirectional reflectionless propagation in the forward direction for GST in its amorphous phase, and in the backward direction for GST in its crystalline phase. Our results could be potentially important for developing a new generation of compact active free-space optical devices

Optimization of photonic nanojets generated by multilayer microcylinders with a genetic algorithm

We employ a genetic algorithm coupled with Mie theory to optimize the magnetic field intensity profile of photonic nanojets (PNJs) generated by multilayer microcylinders at visible wavelengths in free space. We first optimize five-layer microcylinders to elongate the PNJs. We show that a properly designed five-layer microcylinder structure can generate an ultra-long PNJ with a beam length ∼ 107.5 times the illumination wavelength λ0. We then optimize five-layer microcylinders to narrow the waist of PNJs. We show that a PNJ with a full-width at half maximum waist of ∼ 0.22λ0 can be obtained outside the surface of the optimized microcylinder. In addition, curved PNJs with subwavelength waist are also obtained. We finally optimize the five-layer structures for refractive index sensing based on the beam length of PNJs. The estimated minimum detectable refractive index variation when using this sensing method is ultra-small. Our results could potentially contribute to the development of a new generation of devices for optical nanoscopy and biophotonics, and greatly promote the practical applications of PNJs

Neuroimmune cardiovascular interfaces in atherosclerosis

Two pairs of biological systems acting over long distances have recently been defined as major participants in the regulation of physiological and pathological tissue reactions: i) the nervous and vascular systems form various blood-brain barriers and control axon growth and angiogenesis;and ii) the nervous and immune systems emerge as key players to direct immune responses and maintain blood vessel integrity. The two pairs have been explored by investigators in relatively independent research areas giving rise to the concepts of the rapidly expanding topics of the neurovascular link and neuroimmunology, respectively. Our recent studies on atherosclerosis led us to consider a more inclusive approach by conceptualizing and combining principles of the neurovascular link and neuroimmunology: we propose that the nervous system, the immune system and the cardiovascular system undergo complex crosstalks in tripartite rather than bipartite interactions to form neuroimmune cardiovascular interfaces (NICIs)

Switching photonic nanostructures between cloaking and superscattering regimes using phase-change materials

We show that phase-change materials can be used to switch photonic nanostructures between cloaking and superscattering regimes at mid-infrared wavelengths. More specifically, we investigate the scattering properties of subwavelength three-layer cylindrical structures in which the material in the outer shell is the phase-change material Ge_2Sb_2Te_5 (GST). We first show that, when GST is switched between its amorphous and crystalline phases, properly designed electrically small structures can switch between resonant scattering and cloaking invisibility regimes. The contrast ratio between the scattering cross sections of the cloaking invisibility and resonant scattering regimes reaches almost unity. We then also show that larger, moderately small cylindrical structures can be designed to switch between superscattering and cloaking invisibility regimes, when GST is switched between its crystalline and amorphous phases. The contrast ratio between the scattering cross sections of cloaking invisibility and superscattering regimes can be as high as ∼ 93%. Our results could be potentially important for developing a new generation of compact reconfigurable optical devices

Using phase-change materials to switch the direction of reflectionless light propagation in non-PT-symmetric structures

We introduce a non-parity-time-symmetric three-layer structure, consisting of a gain medium layer sandwiched between two phase-change medium layers for switching of the direction of reflectionless light propagation. We show that for this structure unidirectional reflectionlessness in the forward direction can be switched to unidirectional reflectionlessness in the backward direction at the optical communication wavelength by switching the phase-change material Ge2Sb2Te5 (GST) from its amorphous to its crystalline phase. We also show that it is the existence of exceptional points for this structure with GST in both its amorphous and crystalline phases which leads to unidirectional reflectionless propagation in the forward direction for GST in its amorphous phase, and in the backward direction for GST in its crystalline phase. Our results could be potentially important for developing a new generation of compact active free-space optical devices. We also show that phase-change materials can be used to switch photonic nanostructures between cloaking and superscattering regimes at mid-infrared wavelengths. More specifically, we investigate the scattering properties of subwavelength three-layer cylindrical structures in which the material in the outer shell is the phase-change material GST. We first show that, when GST is switched between its amorphous and crystalline phases, properly designed electrically small structures can switch between resonant scattering and cloaking invisibility regimes. The contrast ratio between the scattering cross sections of the cloaking invisibility and resonant scattering regimes reaches almost unity. We then also show that larger, moderately small cylindrical structures can be designed to switch between superscattering and cloaking invisibility regimes, when GST is switched between its crystalline and amorphous phases. The contrast ratio between the scattering cross sections of cloaking invisibility and superscattering regimes can be as high as ~ 93%. Our results could be potentially important for developing a new generation of compact reconfigurable optical devices